The last time his "I want off" article was reposted[0], the comments were pretty rough, ranging from ad-hom attacks to (at best) misunderstandings of the arguments he was making.
I see this article being an address to these criticisms (which are not limited to this forum, I've seen similar arguments on twitter, etc.).
Pointing out shortcomings isn't really impolite or unfair. The author specifically mentioned shortcomings of Rust as well.